Self-Triggering Rotor for Pneumatic Paddle Motor

ABSTRACT

A rotor for pneumatic paddle motor is described, comprising a plurality of segments ( 50 ) separated by radial grooves ( 5 ) adapted to slidably house paddles ( 4 ). Each segment ( 50 ) includes a surface external edge ( 9, 9′ ) consisting of a convex portion ( 10 ) joined to at least one concave abutment ( 11, 11 ′).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Italian Patent Application MI2009A000988, filed Jun. 8, 2009, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a self-triggering rotor for pneumatic paddle motor which may be used on surface processing machines for example, such as surfacers, sanders, and polishers.

BACKGROUND OF THE INVENTION

The rotor is eccentrically contained within a cylindrical housing of larger size than the rotor. The rotor is equipped with vertical radial grooves within which paddles slide in a radial direction. The paddles emerge due to the centrifugal force exerted by the rotor in the area where between the rotor and the housing, there is a spacing allowing the paddles to emerge and retract under the limiting action of the internal cylindrical walls of the rotor housing, in the area where rotor and housing are close to each other, due to the assembly eccentricity between rotor and housing.

The rotor is rotated by a pressurized air flow acting on the rotor paddles. A suitable channelling of the compressed air consisting of radial and circumferential sections and placed in the rotor heads, manages the air from an inlet towards a first paddle by pushing it radially outwards, thus causing the supply chamber to close and triggering the rotation of the rotor.

This solution has the drawback of requiring the heads to be milled for obtaining the triggering channelling, and at speed, of wasting a fraction of the compressed air “forced” to cross said channelling and therefore subject to load losses.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a pneumatic paddle motor which is constructionally simple and capable of optimizing the activating air flow both in the triggering phase and at speed.

In accordance with the invention such an object is achieved by a pneumatic motor as disclosed in claim 1.

These and other features of the present invention will become increasingly apparent from the following detailed description of a practical embodiment thereof; shown by way of non-limiting example in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of a machine with a rotor according to the known art;

FIG. 2 shows a cross-section view of a machine with a rotor according to the known art;

FIG. 3 shows an exploded view of a machine with a rotor according to the invention;

FIG. 4 shows a cross-section view of a machine with a rotor according to the invention;

FIG. 5 shows the enlarged circle A in FIG. 4;

FIG. 6 shows a perspective view of the rotor according to the invention;

FIG. 7 shows a top plan view of the rotor in FIG. 6;

FIG. 8 shows a top plan view of the rotor according to a further embodiment;

FIG. 9 shows a section view according to the line IX-IX in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the accompanying drawings and in particular to FIGS. 1 and 2, a surfacer 100 is shown comprising a pneumatic paddle motor 20 belonging to the known art. Motor 20 is equipped with a rotor 10 with paddles 40, eccentrically contained in a housing 60, adapted to activate a shaft 170. Motor 20 is described in the introduction of the present application. Hereinafter, a brief reminder of the activation of rotor 10 as depicted in FIG. 2 is provided: the compressed air flow from an inlet 70 enters in a milled channel 400 in the upper 140 and lower 150 heads (FIG. 1), thus triggering the rotation.

Said channel 400 consists of a radial section 401 connected to inlet 70 and of a curved section 402 adapted to direct the air towards a housing 60 of a paddle 40.

The heads 140, 150 comprise bearings 200.

A self-triggering rotor 1 according to the present invention for a pneumatic paddle motor 2 is seen in FIGS. 3-7. In particular, in FIG. 3 the self-triggering rotor 1 activating a shaft 17 is denoted, which comprises radial grooves 5 in which paddles 4 adapted to define rotor segments 50 are slidably housed.

Rotor 1 is eccentrically contained in a closed cylindrical housing 6 which comprises an inlet 7 and a return 8 for a compressed air flow.

Said rotor 1 is closed by heads 14, 15 comprising bearings 20.

The heads 14, 15 have no trigger channelling 400.

Said housing 6 is adapted to allow the paddles 4 to radially emerge and retract according to a predetermined, known program: given the assembly eccentricity between rotor 1 and housing 6, as shown in FIGS. 3-7, the spacing between the periphery of rotor 1 and the internal wall of housing 6 varies, and upon the rotation of rotor 1, the paddles 4 emerge due to the action of the centrifugal force when this spacing allows it, and they cyclically retract due to the lack of space, along their rotation.

The inlet 7 directs the compressed air flow over the paddles 4 thus activating the rotation of rotor 1.

Instead of milling the heads 14, 15, the present invention as operated in the known art suggests a particular external profile of rotor 1.

The edge 9 of each segment 50 of rotor 1 consists of a traditional convex portion 10 joined to a following concave abutment 11 ending in groove 5. In the present embodiment, the concavity is radial while a right angle corner may be provided.

The compressed air from inlet 7 functionally enters the housing 6 through a passageway 600, directly interacting with the edge 9 of a first segment 50.

The rotation is then triggered. The rotation is triggered by the rotor itself, from which the definition “self-triggering”,

The profile of said edge 9 described above determines an optimization of the air flow which determines the triggering and an optimal thrust on the paddles 4 due to the concave abutment 11 following the convexity 10.

By entering, the air from the inlet 7 hits the abutment 11 with a direct thrust on the segment 50 of rotor 1 by providing a localized acceleration which is translated into a greater thrust force adapted to trigger the rotation and the consequential emersion of the paddle 4 from groove 5 due to the centrifugal force.

A rotor is shown in FIG. 8, where each segment 50 provides an edge 9′ with two concave abutments 11, 11′ joined to each other by the convex portion 10. This constructional solution allows the assembly in housing 6 to be independent from the rotation direction of the rotor, an abutment 11, 11′ being provided however, for the self-triggering according to the invention.

Moreover, the double abutment 11, 11′, combined with a double inlet 7 with a single discharge 8, allows reversible motors with both right and left rotation directions to be manufactured. The two inlets 7 are placed so as to selectively activate the rotor in opposite directions. 

1. A pneumatic paddle motor comprising a rotor (1) comprising a plurality of segments (50) separated by radial grooves (5) suitable to slidably house paddles (4), said rotor (1) being mounted offset in a cylindrical housing (6) and with rotation axis shifted towards a first edge portion (66) of the housing (6) comprised between an inlet (7) and an outlet (8) of the compresses air in such a way that the paddles (4) are completely contained in said radial grooves (5) in correspondence with said first edge portion (66) and are movable inside said grooves (6) between said maximum containment position and a position of maximum protrusion substantially in correspondence with a second edge portion (67) opposite to said first edge portion (66), the paddles (4) being suitable to perform said movement of coming out and back only one time for every round of the rotor (1), wherein each segment (50) of said rotor provides a superficial external edge (9, 9′) consisting of a convex portion (10) joined to at least a concave abutment (11, 11′).
 2. The motor according to claim 1, wherein said concave abutment (11, 11′) provides a curved cavity.
 3. The motor according to claim 1, wherein said concave abutment (11, 11′) provides a cavity with a right angle corner.
 4. The motor according to claim 1, wherein the surface external edge (9) is constituted by a convex portion (10) joined to a following concave abutment (11).
 5. The motor according to claim 1, wherein the surface external edge (9′) is constituted by a couple of concave abutments (11′) joined between them by a convex portion (10). 